Doctors and public health experts will tell you that, compared to white Americans, African American people die prematurely and disproportionately of many ills: heart disease, stroke, COVID-19, police violence.

The proximate causes of these early deaths vary. But there is a sameness to the pattern, experts say, and a common source of the skewed statistics.

Racism — not in its overt, name-calling form, but the kind woven deeply into the nation’s institutions — harms the 44 million Americans who identify as black and potentially shortens their lives, according to those who study racial inequities in health. For some, including Minnesotan George Floyd, it causes premature death in minutes. For others, a lifetime of disadvantage takes its toll in subtler ways.

“At the end of the day, racism is the original sin here,” said Dr. Georges Benjamin, executive director of the American Public Health Assn. “Racism attacks people’s physical and mental health,” he said. It’s “an ongoing public health crisis that needs our attention now.”

And in the midst of a pandemic, Benjamin and others fear that as crowds fill the streets to protest yet another police killing of an unarmed black man, people of color will again bear the disproportionate brunt of renewed infections.

It is an agonizing trade-off, they acknowledge. But it’s hardly a choice.

“I’ve spent the last several months of my life imploring and exhorting people to protect themselves, to reduce the spread of this virus and save lives,” said Dr. Clyde W. Yancy, a cardiologist at Northwestern University’s Feinberg School of Medicine who is African American. But after Floyd’s death under the knee of Minneapolis police officer Derek Chauvin, he said, “it dawned on me that my greatest risk is not COVID-19. It’s the color of my skin.”

Dr. Atheendar Venkataramani, an internist and health policy researcher at the University of Pennsylvania, has plumbed the power of despair to erode the health of specific American populations. He was part of a team that assessed changes in the mental health of Americans who lived in states where at least one unarmed black man had been killed by police.

In the three months following these deaths, the team found a measurable drop in mental health among black Americans — and the more deaths there were, the greater the effect. Mental health did not suffer in cases when police killed a black person with a weapon.

The mental health of white Americans was not associated with fatal police encounters involving either armed or unarmed black Americans. The findings were published in 2018 in the medical journal the Lancet.

“It’s not like we’re giving them a choice here,” Venkataramani said of the latest spasm of protests. The neglect of African Americans’ economic, social and health problems has been “so pernicious, so ingrained and so predictable,” he added, “how could you not be out there calling attention to these issues?”

In medical language, racism, including the kind baked into so many U.S. institutions, is a toxin. Just like polluted air, chronic stress and malnutrition — all of which often flow from racial injustice — its effect is corrosive.

An African American baby born in 2017 has a life expectancy that’s 3.5 years shorter than that of a white baby. If current inequities persist, the black baby will be nearly 2.5 times more likely to live in poverty, almost twice as likely to leave school before getting a high school diploma and more than six times as likely to be incarcerated than the white one.

Along the way, the average African American will live in poorer housing, have less access to healthy foods and be more exposed to environmental pollutants and violent crime than his or her white counterpart. He or she is more likely to suffer from obesity, asthma, diabetes, heart disease and high blood pressure.

Despite this, studies show that many physicians discount the ills reported by African American patients, engendering a mistrust that often discourages them from seeking prompt medical care.

In recent months, inequities like these have contributed to starkly higher coronavirus casualties among African Americans than white Americans. An analysis of survey data from Johns Hopkins University found that coronavirus infection rates were three times higher in counties with predominantly black populations than in predominantly white ones, and COVID-19 death rates were six times higher.

In both California and New York, African American adults have been overrepresented among COVID-19 deaths by a factor of two. In Michigan, their share of COVID-19 deaths is three times greater than their share of the population.

Bridget Goosby, a University of Texas sociologist who studies health disparities, said the COVID-19 pandemic has left many African American communities in a particularly depleted state.

The “essential worker” designation of many low-wage jobs filled by people of color — delivery drivers, hospital workers, grocery store clerks — had set the stage for many to feel unfairly exposed to danger.

For many, that sense was deepened by stories like those of Deborah Gatewood, an African American phlebotomist in Detroit who died after the hospital where she had worked for 31 years denied her a coronavirus test four separate times, and of Brittany Bruner-Ringo, an African American nurse who was ordered to admit a visibly sick patient to an upscale dementia care center in Los Angeles and died of COVID-19 one month later.

It took months for many states to begin collecting data that confirmed a widely held suspicion: that the pandemic was taking a far heavier toll on blacks than on whites.

Then, in mid-May, data from New York City’s Police Department revealed that 93% of their arrests made to enforce social distancing rules were of black and Latinos. Meanwhile, armed white protesters calling for their states’ “liberation” were hailed by President Trump.

Amid so much loss of life, many of the places African Americans would normally turn to for comfort and strength — including churches and beauty shops — have been closed by the pandemic, Goosby said. Even extended families have been kept apart.

“There’s a collective grief,” she said. “And you’re already deprived of having this social net, of being able to grieve with people. You don’t feel like your grief is acknowledged, or that anything has changed.”

Into this tinderbox of pain, throw the match of Floyd’s graphically documented killing.

To anyone who has been paying attention, “nothing about this is surprising,” Goosby said.

In a recent essay in the Journal of the American Medical Assn., Yancy wrote that COVID-19’s heavy toll on African Americans had brought forth a long-awaited “moment of ethical reckoning.”

The United States “has needed a trigger to fully address healthcare disparities,” he wrote. “COVID-19 may be that bellwether event.”

Now the country’s ethical reckoning is more urgent than ever.

“How does a civil society — if indeed we are civil — respond not only to disproportionate suffering but also to a legacy of injustice?” Yancy said. “We will soon know the character of our populace.”

In spite of recent events, he insisted that he remains an optimist.

“One can only hope,” he said.

Los Angeles County extended its sweeping curfew for a third day on Tuesday as protests over police brutality and the death of George Floyd continued across Southern California.

The curfew will be in effect from 6 p.m. Tuesday until 6 a.m. Wednesday, officials said.

The order to keep people at home comes after the Los Angeles Police Department’s Hollywood Division made more arrests Monday than on any single day in history in response to protests that devolved into a series of looting incidents, mostly in Van Nuys and Hollywood.

Officers took at least 585 people into custody Monday. Most arrests were for curfew violations, but officers detained 20 people on suspicion of looting and impounded 50 vehicles, a law enforcement source told The Times on Tuesday.

Authorities had taken approximately 2,500 people into custody between Friday and Tuesday morning after a mix of peaceful protests and property destruction rocked downtown, the Fairfax District, Van Nuys and Hollywood, according to LAPD Chief Michel Moore.

“Each day has seen the continuation of peaceful protests, but we have seen instances of burglaries and looting of businesses in various parts of the city,” Moore said. “For the first time in decades, every sworn member of the Los Angeles Police Department is working. Days off have been canceled.”

Booking records reviewed by The Times show the vast majority of those arrested in L.A. County on looting, vandalism and burglary charges are county residents, seeming to refute perceptions of “outside agitators” coming in to fuel unrest.

Long Beach Mayor Robert Garcia blamed looting and nearly 100 small fires in his city on organized criminals unaffiliated with peaceful protests.

“It’s pretty clear, given the type of activity and how organized the activity was, there is a strategy going city to city and doing this criminal work,” Garcia said this week. The damage to small business owners, he said, was unacceptable.

Demonstrations large and small continued Tuesday throughout California as protests ignited by Floyd’s death showed no signs of slowing.

An independent autopsy commissioned by Floyd’s family this week found he died of asphyxiation caused by neck and back compression after a Minneapolis police officer pinned him to the ground with a knee on the handcuffed man’s neck for several minutes.

Hundreds of protesters, many holding signs, gathered at Hollywood Boulevard and Vine Street late Tuesday morning. After a few minutes, the group began walking through the streets of Hollywood, where they approached a line of several dozen officers holding batons. The officers blocked the crowd’s advance.

“Let us walk,” the crowd yelled. Chants of “I can’t breathe” and “No justice, no peace” echoed throughout.

Aijshia Moody, 30, was among the crowd, holding a cardboard sign that read, “Am I next?” Her brother is 14 years old and has often dealt with racial profiling in Pacoima where they live, she said.

“He can’t even get on his skateboard,” she said, adding that she’s dealt with racism throughout her life. “That’s why I’m here.”

Walking alongside the crush of protesters, community organizer Pete White briefly stopped in front of a Chase bank branch to snap a photo of a scrawled message: “Chase yo dreams.” Nearby, Kendrick Lamar’s “Alright” and N.W.A’s “F— tha Police” blasted from a speaker.

“State violence brings me out here today,” said White, who turned 49 Tuesday.

“We see the signs that say ‘Justice for George Floyd,’ but also, when you see the kaleidoscope of faces, it’s justice for immigrants, it’s justice in thinking that housing is a human right,” said White, a South L.A. resident and founder of the Los Angeles Community Action Network.

There is no peace without justice, he added.

“How do you get justice? By making sure you defund the police and take all of those resources and put it in schooling, put it in services, in housing, in universal healthcare,” White said. “We’re saying we don’t need another commission, another study or implicit bias training. We’ve been there and the same thing keeps happening. Again and again.”

In addition to the countywide curfew, three cities in L.A. County have opted to extend their own curfews through at least Wednesday morning.

Beverly Hills will be under curfew from 1 p.m. Tuesday till 5:30 a.m. Wednesday. Police will be “actively patrolling” the city, including residential areas, officials said.

“I know we are all feeling a great sense of uncertainty tonight,” Beverly Hills Mayor Lester Friedman wrote in a statement. “We are grateful to the National Guard and our mutual aid partners from several neighboring agencies for helping us to keep our community safe.”

In Torrance, officials have imposed a curfew from 6 p.m. to 6 a.m. daily for as long as L.A. County is under a state of emergency. Los Angeles city officials and Gov. Gavin Newsom declared the emergency shortly before midnight Sunday after protests in the Fairfax District turned violent and widespread looting erupted.

In Santa Monica, where several businesses were vandalized and looted on Sunday, a curfew went into effect at 2 p.m. Tuesday and will last till 5:30 a.m. Wednesday.

Santa Monica police made 41 arrests Monday after taking 438 people into custody Sunday. The city also recorded 347 damage reports, including 84 for graffiti, with the majority affecting retail businesses. More than 150 buildings sustained significant damage, city officials said Tuesday.

“If you were out around our city Monday morning, as I was, you know our streets were full of residents with brooms and sweepers. Volunteers cleaned graffiti off walls. The resilient spirit of our city was evident everywhere. Even after the shocking events of Sunday, it is again great to be a Santa Monican,” Mayor Kevin McKeown said.

Under the curfews, people are prohibited from being on streets and sidewalks or in parks and other public spaces. The restrictions do not apply to law enforcement, first responders, people traveling to and from work, or individuals seeking medical care. While the county curfew applies to all cities and unincorporated areas, individual cities can impose stricter limits.

After peaceful protests across the region, the situation escalated in Hollywood and Van Nuys on Monday evening when numerous stores were looted.

Newsom implored Californians to show empathy to one another in his first news conference since he deployed the California National Guard to Los Angeles early Sunday, marking the third time in more than half a century that troops had responded to unrest in the city over violence against a black person in police custody.

“You’ve lost patience. So have I. You are right to feel wronged. You are right to feel the way you are feeling,” Newsom said to protesters, adding: “Society has a responsibility to you to be better, and to do better.”

Just after 1 p.m. in Hollywood, dozens of activists chanted, “Take a knee” at members of the National Guard. After several minutes, at least two Guardsmen complied.

The crowd cheered.

Other protesters encountered a line of police officers and began chanting, “Walk with us,” and “Let us walk.” The group was trying to reach another crowd of demonstrators farther up Hollywood Boulevard, past Cherokee Avenue.

The marchers were met with a line of at least 20 LAPD officers who wouldn’t let them pass. As the group neared the line, their hands up, police began raising their batons to hold them back.

One protester placed a white flower in an officer’s pocket. The officer threw it to the ground.

A segment of the protest hit a snag later Tuesday afternoon as part of the crowd that had gathered near Ivar Avenue and Hollywood Boulevard surrounded police.

The confrontation came after law enforcement received a radio call about armed looters, authorities said. Protesters began throwing bottles and sticks in response to a growing police presence. Officers then fired rubber bullets.

As police pushed the crowd down Ivar, they confronted two women in a red pickup. The driver did not want to stop or put her keys on the dashboard as police tried to pass by, officers said. She was quickly detained.

“We don’t need a confrontation,” one officer later said into megaphone. “Leave the area.”

“Get out of the street, you can continue with your peaceful protest,” he continued.

Another officer, who declined to give his name, acknowledged that the protest had mostly been peaceful.

“Just a few people who ruin it for everybody else,” he said.

Heaven Bouldin had been demonstrating for several hours as curfew neared.

At 25, she said, she has been protesting for 10 years.

“I’m tired, I’m tired, I’m tired,” she said, holding a sign that read, “Stop killing black people.”

“My people have been getting killed for the last 200 years. We’re in 2020 and we still can’t bring an end to this,” she said. “Somebody has to do something.”

On North Cahuenga Boulevard in Hollywood, police were standing in a line blocking the road as a crowd chanted and screamed at them. One woman shouted: “All of you … are found guilty. You violent criminals. All of this because y’all don’t want to stop killing black people. You treacherous snakes!”

One officer, using a megaphone, approached the protesters to announce that they were standing in a line to protect businesses that had been looted.

“We understand why you’re here,” the officer said before assuming his position in the line again.

When the crowd began chanting, “Take a knee! Take a knee!” at the officers, the woman screamed, “We will not take a knee!” and charged toward officers, the yellow caution tape stopping her. “Back up sis!” A young woman told her.

The woman explained, emotionally, why they should not ask the officers for a knee. “I’ve been doing this longer than you’ve been alive,” she said. “Y’all are stupid…. They already took a knee … and they took a life. This don’t look like that to you?” she said, taking a knee herself and raising her fist in the air. “Y’all are … ignorant. This ain’t a time to take a knee.”

The crowd stopped the chant, then started a new one: “Say his name! George Floyd!”

The afternoon was filled with similar moments. Protesters were angry and faced officers and National Guard members throughout Hollywood, but the demonstrations remained largely peaceful.

On Sunset and Vine, two large groups of protesters cheered on each side of Sunset as they joined together, blocking the intersection. Honks and the revving of engines were incessant, and hip hop and rap music sounded throughout the intersection.

Times staff writers Richard Winton, James Queally, Matthew Ormseth, Laura J. Nelson, Gustavo Arellano, Seema Mehta, Taryn Luna, Luke Money, Alene Tchekmedyian, Julia Wick, Jaclyn Cosgrove and Anita Chabria contributed to this report.